Self-cleaning track snow pad for track laying vehicles



Oct. 28, 19.69 M. w. KAIFESH 3,475,060

SBLF'CLEANING TRACK SNOW PAD FOR TRACK LAYING VEHICLES Filed June 4. 1,968

- l MIC/Mil K4 (ll/ff! I I v INVE TO 68 BY ai H64 70 WW Kg United States Patent O 3,475,060 SELF-CLEANING TRACK SNOW PAD FOR TRACK LAYING VEHICLES Michael W. Kaifesh, Warren, Mich., assignor to the United States of America as represented by the Secretary of the Army Filed June 4, 1968, Ser. No. 734,280 Int. Cl. B62d 55/26, 25/00; B60s 1/62 US. Cl. 305-13 Claims ABSTRACT OF THE DISCLOSURE A self-cleaning track shoe assembly for a tracked vehicle designed for preventing snow from packing in the track pad cavity of the shoe so that the vehicle is operable when traversing snow or ice. Novel track pad adaptors are located in each shoe cavity which incorporate resiliently compressible means; the arrangement being such that after each successive compression loading by the road wheels, snow is forced from the track pad cavity by way of the pad springing back to its uncompressed position.

The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to endless tracks for track-laying vehicles and is particularly concerned with a replaceable self-cleaning track pad for adapting conventional track shoes for traversing snow or ice to obtain maximum vehicle performance.

Description of the prior art The prior art, as exemplified by US. Patent No. 3,017,225 issued J an. 16, 1962, discloses the construction of track shoes for a vehicle endless track wherein the track pad projects a predetermined amount beyond the track shoe grouser ribs so that when the shoe lies on hard flat ground, the rubber pad alone makes contact with the ground. The purpose of this arrangement is to protect the road surfaces by having the track move on rubber pads while also reducing wear of the track shoe.

It is well known that when the above mentioned type of track shoe is used on track vehicles operating under winter conditions traversing snow, the ground pressure of the shoe is low because the grouser ribs cannot penetrate the snow and therefore fail to provide the aggressiveness required for the desired mobility. However, when the conventional track pads are removed to increase ground pressure, the snow fills or packs the track pad cavities resulting in a duplication of unwanted low ground pressure condition described for shoes equipped with conventional track pads.

SUMMARY Applicants solution to the problem involves the installation of a self-cleaning track shoe pad arrangement for adapting a track vehicle for traversing snow which prevents snow from filling or packing the track pad cavity. The present application discloses two embodiments for accomplishing this result. The first embodiment uses an independent mechanical spring means sealed within a hollow pocket provided in the pad while the second embodiment uses a resilient elastomer block-type pad defining one or more compressible chambers located in the block.

In each case the pad assembly is recessed in the shoe 3,475,060 Patented Oct. 28, 1969 cavity defined by the track shoe grouser ribs to provide a resilient member covering the cavity base. Under high loading conditions, when the track shoe passes directly under one of the vehicle road wheels, the resilient pad will flex inward from the force transferred by the packed snow. After the vehicle load is released, due to the road wheel passing on to the adjacent track shoe, the pad will spring back to its unloaded position thereby expelling the snow from the cavity. The track shoe grousers are thus free to penetrate the snow or ice to provide the aggressiveness required for obtaining maximum track vehicle performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 shows a plan view of the track shoe link;

FIGURE 2 is a partial section taken on line 22 of FIGURE 1 showing applicants track pad in place;

FIGURE 3 is a plan view of a second embodiment of applicants invention for use with the track shoe of FIGURES 1 and 2;

FIGURE 4 is a cross section of the pad of FIGURE 3 taken on line 44 with the grouser portion of the shoe shown in phantom lines;

FIGURE 5 is a cross-section taken along the line 55 of FIGURE 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, there is shown in FIGURE 1 a conventional single pin track shoe generally indicated at 10 which includes a bar-like bushing pin 12 extending therethrough and threaded at one end for the reception of a securing nut 14 such that adjacent shoe plates can be locked one to another. Each track shoe is formed by a unitary structure having a metal base portion 16 including a first row of bearing bosses 18, 20, and 22 or one long side of the shoe body and a second row of staggered bearing bosses 24 and 26 on the opposite long side. This arrangement allows one track shoe to move out of the plane of the next adjacent shoe through a turning movement of the resilient bushings 28 of the bearing bosses.

On the upper surface of the base 16 there is provided a track pad cavity 30 formed by the longitudinal and transverse grouser ribs 32, 33 and 34, 35 respectively, formed integral with the base. Although in the instant embodiment of the invention the cavity 30 is rectangular in plan, it is to be understood that the cavity could have various configurations, such as triangular or circular for example, without departing from the scope of the present invention.

The track pad adaptor, generally indicated at 36, comprises a composite hollow block having an upper wall 37, formed with-a substantially flat elastomer outer portion 38 and rigid metal backing plate inner wall 39, and a lower rigid wall 40 bonded or otherwise sealed to the depending elastomer side walls 38a of the pad 36. The margins of the metallic wall 40 are preferably turned to provide a flange 40a extending upwardly along the margins of the pad to provide a greater surface for bonding the metal to the elastomer side walls 38a. The pad 36 is detachably mounted in the cavity 30 by conventional fastening means such as the threaded round head bolt 42 and unshown securing nut.

In this manner, the pad 36 is thus fabricated to provide a sealed pocket or chamber 46 having resilient spring biasing means generally indicated at 48 sandwiched between the upper and lower walls 37 and 40 of the pad. It will be noted that the backing plate 39' is formed to be coextensive with the horizontal undersurface of the elastomer portion 38 and bonded thereto to provide a bearing surface for the spring biasing means,

which in the instant embodiment is shown as a single leaf spring extending substantially throughout the length of the pocket 46. It is to be understood that other mechanical spring means such as coil or Belleville type springs are contemplated by the inventor in place of the leaf spring depending upon space limitations and shape of the shoe.

As seen in FIGURE 1, the leaf spring 48 has the general form of a dumbbell when viewed in plan having a pair of vertically offset wings 54 and 56 so as to exert substantially equal pressure at each end of the upper wall 37. Suitable means, such as the head portion of the bolt 42, are provided for securing the central portion of the leaf spring 48 to the lower wall 40 of the pad. A bore 50 is provided in the shoe base 16 for reception of the bolt 42.

By means of the above described track shoe assembly the space 30 intermediate the grouser ribs 32, 33, 34, and 35 and above the upper wall 37 define a portion of the pad cavity that is left free and unobstructed. It will be noted in FIGURE 2 that the pad 36 has an overall vertical height, indicated by the dimension X, that is substantially less than the overall vertical height of the grouser ribs 32-35 indicated by the dimension Y. In the embodiment of FIGURES 1 and 2, the dimension X is of the order of one and one-quarter inch (1% inch) while the dimension Y is of the order of two inches (2 inches). The result is that approximately three-quarters of an inch of the upper portion of the grouser ribs is free to penetrate the snow over which the tracked vehicle is moving.

As the space 30 becomes packed with snow it will be apparent that when each shoe is subjected to high loading conditions due to the shoe moving directly beneath a roadwheel the upper wall 37 of the snow pad will flex inwardly. When the vehicle load is released from the shoe, the upper wall 37 will spring back to its original position thereby expelling the snow from the pad cavity.

Turning now to the form of the invention shown in FIGURES 3, 4 and 5, a modified track snow pad indicated generally at 60 is shown, and which is constructed from an elastomer material having substantially parallel inner and outer surfaces indicated at 62 and 64. The inner surface 62 has a rigid plate 66, formed of metal or the like, bonded thereto. The plate 66 has suitable fastening means such as bolt 68 for insertion through the bore 50 of the track shoe of FIGURES 1 and 2 to receive a threaded nut (not shown). The margins of the plate are again preferably turned to provide a flange 66a extending upwardly along the margins of the pad to provide a greater surface for bonding the metal to the rubber.

The inner surface 62 of the pad 60 has a large number of closely adjacent substantially parallel cored chambers 70 extending a portion of the distance from the inner surface 62 to the outer surface 64 of the pad. These chambers define resiliently compressible voids between adjacent projections formed by the elastomer mentioned. This arrangement imparts a limited degree of flexibility to the pad when subject to the pressure of the vehicle road wheels transmitted by the packed snow within the track snow cavity.

In the particular embodiment shown in FIGURES 3-5, the elastomer block or pad comprises a 100 percent synthetic rubber compound being comparatively soft in relation to the hard rubber compound used for conventional track pads. The hardness of the composition should for best results be from 40 to 60 Shore Durometer Hardness Type A. This is to be compared with the normal military specification track pad Shore Durometer Hardness rating which falls within the range of 60 to 75. It should be noted that the chambers 70 are of a size which depends upon the particular dimension of the track shoe, weight of the track vehicle etc., and in the instant case have a diameter of approximately three-quarters of an inch and an equal depth so as to extend more than onehalf the total thickness of the pad.

The resilience of the pad 60 may be correctly predetermined by selecting the desired size and number of the chambers as well as the Shore A Durometer Hardness reading of the material. It will be understood that the chambers could be rectangular or hexagonal, for example, instead of circular and also could be placed in various arrangements in place of the staggered relation shown without departing from the scope of the invention. It is also contemplated that the chambers could be molded so as to be completely incased Within the pad thereby being sealed against the entrance of moisture or other foreign material. The elastomer portion of the pad insert of both embodiments of the invention may be of any suitable semi-soft molded rubber material such as natural or synthetic rubber of the like.

As best seen in FIGURE 3, the pad 60 is intended to be inserted in a standard track shoe cavity such as provided by the track shoe shown in FIGURE 1. The pad 60 is recessed below the grousers of the shoe, indicated by phantam lines in FIGURE 4, a predetermined amount in a similar manner as shown by the pad 36 of FIGURE 1. The operation of the pad 60 is essentially the same as that described for the pad 36 in that it flexes inwardly when a roadwheel passes directly over the track shoe inducing a high loading condition on the snow packed within the cavity. When the load is released by the track pad moving away from the roadwheel, the pad will spring back to its original position, to thereby dislodge the snow from the track shoe.

It will of course, be understood that other types of tracks such as the double pin type and flexible cable reinforced band tracks could use applicants self-cleaning pad in addition to the single type pin.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A self-cleaning shoe assembly in combination with an endless track, comprising:

(a) a metal track shoe having a plurality of spaced projecting grouser ribs forming an enclosed hollow track pad cavity therebetween and including a bottom wall in said cavity,

(b) resilient track pad means including a metal plate portion seated on said bottom wall in said cavity,

(c) said track pad means disposed below said grousers such that the space intermediate the grouser ribs and above said pad means bounding such space is free and unobstructed, and

(d) said pad means including spring means between said plate and the outer surface of the pad resiliently biasing said upper portion away from said plate.

2. The track shoe assembly as defined in claim 1, wherein:

(a) said track pad means comprising an elastomer 'hollow block upper portion defining with said bottom plate portion a pocket therebetween said spring means in said pocket.

3. The assembly as defined in claim 2, wherein a second rigid plate means is bonded to the underside of said upper elastomer portion.

4. The assembly as defined in claim 2, wherein said spring biasing means is a leaf spring.

5. The assembly as defined in claim 4, wherein said leaf spring comprises a pair of offset wings, one engaging either end of said second rigid plate means to absorb loads applied to said elastomer upper portion.

6. The track shoe assembly as defined in claim 1, wherein, said track pad means comprises an elastomer block having a plurality of voids formed therein, whereby to impart a limited degree of flexibility to said track pad. 7. The track shoe assembly as defined in claim 6,

wherein the plurality of voids are aligned chambers extending more than one-half the distance from the inner surface to the outer surface of said block.

8. The track shoe assembly as defined in claim 6, wherein said block is a synthetic rubber compound having a hardness from 40 to 60 on the Shore Durorneter Hardness Type A scale.

9. The track shoe assembly as defined in claim 7, wherein said plurality of voids are substantially parallel chambers having a circular cross-section.

10. The track shoe assembly as defined in claim 9, wherein said chambers are formed with their diameters and depth substantially equal.

References Cited UNITED STATES PATENTS RICHARD J. JOHNSON, Primary Examiner SOS-35, 46

U.S. Cl. X.R. 

